Method of and apparatus for forming internal threads in a workpiece



Feb. 13, 1940. G. H. HAGERMAN 2,189,857

METHOD OF AND APPARATUS FOR FORMING INTERNAL THREADS IN A WORKPIECE Filed July 18, 1958 s Sheets-Sheet 1 I v I j [$7, Zhmmtor Feb. 13, 1940.

G. H. HAG ERMAN METHOD OF AND APPARATUS FOR FORMING INTERNAL THREADS IN A WORKPIEGE Filed July 18, 1938 3 Sheets-Sheet 2 Jnnmtor attorney S Feb. 13, 1940.

G. H. HAGERMAN METHOD OF AND APPARATUS FOR FORMING INTERNAL THREADS IN A WORKPIEOE Filed July 18, 1958 3 Sheets-Sheet 5 Snuentor Patented Feb. 13, 1940 UNITED STATES METHOD OF AND APPARATUS FOR FORBI- ING INTERNAL THREADS IN A 'WOBK- PIECE Gilbert H. Hagerman, Dayton, Ohio, assignor, by mesne assignments, to Societe d'Exploitation des Brevets Moineau, Luxembourg, Luxembourg Application July 18, 1938, Serial No. 219,712

6 Claims. (G1. 10-154) ,This invention relates to a method of and apparatus for manufacturing one of the two helical members employed in the gear mechanism described in United States Letter Patent No.

1,892,217, dated December 27th, 1932 to R. J. L. Moineau, and United States Letters Patent No. 2,028,407, dated January 21st, 1936, to the said inventor, the particular helical member for which this invention is adapted being that which will be hereinafter termed the stator as distinguished from the rotor and on which the helical threads are turned on the interior surface thereof.

In those two United States patents there is described a gear mechanism particularly adapted for pumps for fluids consisting of two helical members disposed one within the other and as before stated this invention relates to a method and a mechanism for carrying out the method 30 such as a milling machine for boring or milling the bore of the stationary helical member, for the purpose of equipping the bore with at least two helical independent threads, orinother words a double thread depending on the numher of threads of the rotor.

One of the objects of the invention is to provide a method and apparatus for forming a helically-threaded stator of the character described which will be simple in construction, eco-' nomical in manufacture, and effective for the purpose for which it is designed.

A further and more specific object of the invention is to provide a mechanism in the form of a milling machine which will provide for 5 rotating the workpiece, which in the present case is the stator referred to, upon its own axis and also provide for moving the workpiece in a direction parallel with its axis of rotation, the speed of rotation of the workpiece upon its own 40 axis and the feed of the workpiece in the direction of its axis being slow and predetermined, and being in timed relation with each other.

A further object of the invention is to provide a method and mechanism whereby a cutter is 45 inserted in the bore of the workpiece and has imparted thereto a series of rapid oscillatory movements to bring it in efiective cutting relation with the interior bore of the workpiece, the cutter being held against longitudinal 50 movement in the direction of the axis of the workpiece; the distance or length of the oscillatory movement of the cutting tool being predetermined with relation to the bore of the particular sized stator which is being operated upon.

5 In the accompanying drawings:

Fig. 1 is a front elevationpartly in section and partly broken awayof an apparatus employed in carrying out the method.

Fig. 2 is a. side elevation of the same looking from the right in Fig. 1. Fig. 3 is a side elevation of the same looking from the left in Fig. 1.

Fig. 4 is an enlarged section of some of the parts shown in Fig. 1. r

Fig. 5 is a. front elevation of the cam which 1 reciprocates the cutter.

Fig. 6 is a side elevation of the cam shown in Fig. 5.

Fig. '7 is a front elevation of the cam which reciprocates with cutter showing its'relation with the blocks with which it cooperates.

Fig. 8 is a side elevation of the cam and blocks shown in Fig. '7.

Fig. 9 is a section on the line 9-9 of Fig. 1.

Referring to the drawings all of the mechanism 20 is supported by a standard I which has a later ally-projecting and vertically adjustable shelf 2,

this shelf being adjusted by the screws 3 and I and hand wheel 5 through suitable mechanism in a well known way, not shown-in the present .25 case, the screw 3 being threaded in an upwardly projecting hollow boss 3 in the usual way and the screw threaded in the screw 3; the shelf sliding upon suitable vertical ways 6 on the standard. A table I is slidably mounted on the 30 shelf for horizontal movement, this table sliding upon ways 8 on the upper side of the shelf. The table is adjusted horizontally by a hand wheel 8 through the medium of a screw not shown, .but which is yvell known in milling machines.

The table I carries a bearing member in in which is journalled a spindle II which is adapted to receive the workpiece l2, which in the present case is the stator of the pump described in the patents referred to. The inner-"end of the spindle II has an annular flange l3 and before it is inserted in the bearing a bushing I4 is slipped thereon and a worm wheel I5 is connected therewith, the bearing being counterbored to receive the worm wheel and bushing, the bushing after being inserted having a tight fit in the hearing so as to hold the parts in assembled relation. The workpiece may be held in the spindle in any suitable way such as the clamps l3 shown in Fig. 4.

The worm wheel l5 meshes with the worm it connected with a shaft H, the lower portion of the bearing being chambered out to receive the worm wheel and also to provide for bearings il' in which the shaft I l is iournalled. The shaft i (not shown).

a shaft 32 through the medium of sprocket wheels 33 and 34 and sprocket chain 35 so that has connected therewith just outside the bearing a miter gear l9 which has meshing therewith a miter gear 20 connected with the end of a shaft 2|. The shaft 2| is journalled in two brackets 22 carried by the table 1. Connected with the other end of the shaft is a spur gear 23 which is driven from the spur gear 24 through the medium of the idler gear 25. The gear 24 is connected with one end of a lead screw 26. The lead screw is connected with the shaft 21 through the medium of spur gears 28 and 29. The shaft 21 is driven in any suitable way from a spindle 30 which has a series of different sized cone pulleys 3|, so that the shaft 27 may be driven at different speeds from line shafting and a belt This spindle 30 is connected with the shaft 32 derives power from the spindle. The shaft 32 leads into a gear transmission casing 36 which has suitable change-o-f-speed gearing therein not shown in the present case as it is well known. This gearing connects through a universal coupling 37 with a shaft 38 which is universally connected by a coupling 39 with suitable reverse gearing (not shown) in the box 40. The gearing in this box 40 is connected with the shaft 21 by connections shown in dotted lines in Fig. 2 in which 56 represents a spur gear in the box 40 which meshes with a spur gear 51 on the shaft 58 which hasa beveled gear 59 meshing with a beveled gear 60 on the shaft 6| which has a worm gear 62 meshing with a worm 63 on the shaft 21.

By these connections a very slow feeding movement is imparted to the table 1 which supports the bearing and spindle for the workpiece and also a slow predetermined speed is imparted to the workpiece to rotate it upon its own axis.

The ratio of the gearing and driving connections is such that the workpiece will be fed throughout the length of one pitch distance of either thread during one revolution thereof.

The cutter is indicated at 4|, the cutter being a circular cutter which has an annular sharp cutting edge. The cutter is connected with an arbor 42, one end of which is journalled in a bearing 43 carried by a slidable bracket 44 by webs 45, this bracket being made manually adjustable for the purpose of assembly. The other end of the arbor 42 is connected with a chuck 46 which is connected with an electric motor 41 through the medium of any one of a scrim of grooved pulleys 48 connected with a shaft 49 connected with the chuck, belt 50 and grooved pulley which is connected with the shaft 52 of the motor. The driving mechanism serves 'to impart a rapid rotary movement to the arbor and thus to the cutting tool.

In addition to the rotary movement imparted to the cutter a reciprocatory movement is also given thereto. The spindle 30 heretofore described has keyed thereto a cam 53 which rotates between a pair of metal blocks 54 bolted to a reciprocatory slide 55 which slides upon the ways 6 heretofore referred to. This slide also has connected therewith the bracket 44 heretofore referred to as supporting the bearing 43 with one end of the arbor 42. This arrangement imparts a reciprocatory movement to the cutter 4| within the bore of the workpiece.

When the tool starts to cut the stator it cuts a substantially elliptical bore in the beginning and as the stator moves past the tool, the tool continues to cut an elliptical bore'with the major axis in a vertical position. At all times this form would be an ellipse at any transverse section where the tool is cutting and as the stator or workpiece passes the tool the portion that has already been cut may change its position. This results in a double helical thread. When the tool is cutting the upper end of the ellipse it cuts a half-circle and in travelling downward the tool being the same diameter as the minor axis of the ellipse cuts substantially straight sides and then when cutting the lower portion of the ellipse cuts another half-circle similar to that at the upper point.

While the construction shown and described contemplates the cutting of a double thread in the bore of the workpiece, yet it is also applicable to an arrangement in which a single thread may be cut in which case the reciprocation of the tool will be eliminated and the tool engaged with but one side of the. bore of the workpiece. In cutting a double thread it will be understood that the distance of reciprocation of the tool is equally divided from the center of the axis of the workpiece. In either case however whether a double or single thread is cut the workpiece is rotated on its own axis'and fed in the direction parallel to its axis at a predetermined rate of speed into the cutter.

Having thus described my invention, I claim:

1. The method of forming spiral threads in a bore of a workpiece consisting in slowly rotating the workpiece, slowly feeding said workpiece the length of one pitch distance of a thread during one revolution of the workpiece, and cutting diametrically opposite sides of the bore of the workpiece during such rotation and feeding movement of the workpiece by a rotating cutter, and laterally reciprocating the cutter simultaneously with the rotation of the workpiece.

2. The method of forming spiral threads in a bore of a workpiece consisting in slowing rotating the workpiece, slowly feeding said workpiece the length of one pitch distance of a thread during one revolution of the workpiece, and cutting the bore of the workpiece during such rotation and feeding movement thereby by a rotatable cutter, and reciprocating said cutter to bring it alternately in operative relation with the bore of said workpiece thereof.

3. In a machine for forming spiral threads in a bore of a workpiece, a member to hold the workpiece, means for slowly rotating said member, means for slowly feeding said member the 4 length of one pitch distance of a thread during one revolution thereof, a cutter in the bore of the workpiece, means to rotate said cutter, and means to rapidly reciprocate said cutter to bring said cutter alternately in operative relation with the bore of said workpiece at diametrically opposite points thereof during the rotation of said workpiece.

4. In a machine for forming spiral threads in a bore of a workpiece, a support, a table slidably mounted upon said support, a bearing carried by said table, a spindle for carrying the workpiece rotatably mounted in said bearing, means to slowly rotate said spindle, means to slowly feed said table the length of one pitch distance of a thread during one revolution of said spindle,

a circular cutter in the bore of said workpiece immovable in the direction of the feeding movement of said member, means to rotate said cutter, and means to rapidly reciprocate said cutter at diametrically opposite points to bring said cutter alternately in operative relation with the bore of said workpiece at diametrically opposite points thereof during the rotation of said workpiece.

5. In a machine for forming spiral threads in a bore of a workpiece, a base, a table slidably mounted upon said base, a bearing carried by said table, a spindle for carrying the workpiece rotatably mounted in said bearing, means to slowly rotate said spindle, means to slowly feed said table the length of one pitch distance of a thread during one revolution of said spindle, a cutter in the bore of said workpieceimmovable in the direction of the feeding movement of said member, means to rotate said cutter, and means to rapidly reciprocate said outter to bring said cutter alternately in operative relation with the bore of said workpiece at diametrically opposlte points thereof, said means comprising an arbor upon which the cutter is mounted, a slidable support for said arbor, and a cam to reciprocate said support during the rotation of said workpiece.

6. The method of forming a double helical internal thread in the bore of a workpiece consisting in rotating the workpiece on its own axis, feeding the workpiece parallel to its axis at a predetermined rate of feed into a rotating cutter, and rapidly oscillating the cutter at right-angles to the axis of the workpiece at an equal distance on each side of the center of the axis of the workpiecesimultaneously with the rotation of said workpiece.

GILBERT H. HAGERMAN. 

